It was recalled that the quantitative measurement and analysis of structural parameters had shown that, for various metals and processes, the microstructural evolution followed a universal path of grain sub-division; down to the nanoscale. This behavior permitted analysis of the formation and evolution of graded nanoscale structures produced by sliding. Transmission electron microscopic studies and scaling analyses of such structures revealed the predominant role which was played by dislocations in the development of deformation microstructures at multiple length-scales. The crucial role played by dislocations was monitored by high-resolution electron microscopic analysis. This revealed the presence of a large number of glide dislocations, in layers between geometrically necessary boundaries, with individual spacings which were as fine as 5nm.

Deformation Structures Developing on Fine Scales. D.A.Hughes, N.Hansen: Philosophical Magazine, 2003, 83[31], 3871-93